Grinder for the knives of tobacco cutting machines



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GRINDER FOR THE KNIVES 0F TOBACCO CUTTING MACHINES Filed June 18. 1954' I 4 Sheets-Sheet 1 I nwm ro/es 7 kW I v M 7. M 4

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GRINDER FOR THE KNIVES OF TOBACCO CUIEFING MACHINES 4 Sheets-Sheet 2 Filed 7 June 18. 1954 I/VVENTORS B2 WLWJLMMLW ATTDRNEYS Jul p, 1957 D; w. MOLINS E'IAL 2,798,346

GRINDER FOR THE KNIVES OF TOBACCO CUTTING MACHINES 4 Sheets-Sheet 3 Filed June 18. 1954 mwvroes B1. ,w, W19

' A-TTMNEXS July 9, 1957 n w. MOLINS VETAL 2,798,346

GRINDER FOR ms KNIVES 0F TOBACCO CUT-TING MACHINES 'Filed June 18. 1954 4 Sheets-Sheet 4 /.U1'. j w L w 5;

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United States Patent 1c:

GRINDER FOR THE KNIVES F TOBACCO CUTTING MACHINES Desmond Walter Molins, George Smith, James Arthur Mason, and Felix Frdric Ruau, .Deptford, London, England, assignors to Molins Machine Company, Limited, L'o'n'tlon, England, a British company Application June 18, 1954, Serial No. 437,600

Claims priority, application Great Britain June 25, 1953 2 Claims. (Cl. 51-247) compressed tobacco leaves is fed and cut thin slices from the end of the cheese. -It is'iiece ssary to keep the knives of these machines very sharp as "the work is extremely heavy and in the machines as hitherto made the blades pass across the end of a cup grinding wheel at every revolution of the head. The wheel is 'cbnstantly tr-ued by a diamond and advanced fo'tak'e up wear so that the wheel face is always in the "cutting plane or the knives. This construction has several disadvantages, for example, the wheel face is fairly small and the dust resulting from grinding is liable to get into the "cut tobacco besides which the knives are not ground as perfectly as is desirable. This is because a considerable area of knife is pressing on the wheel for grinding at any given instant, and this causes considerable heatan'd although the ground surface is 'quite flat the edge is not always as sharp as is desirable, particularly when a fairly coarse knife feed is engaged.

According to the invention there is provided a machine of the kind referred/to wherein the knives pass over'the curved surface of a grinding wheel which surface is a tangent'to the cutting plane and is so located with respect to the path of the knives and their orientation with respect to the axis of rotation of the cutter head that successive points along a knife edge make grinding contact with the wheel along a straight line. In practice the wheel is cylindrical and the contact line is a straight line on the cylinder parallel to the axis. This construction provides a generall more satisfactory grinder by arranging the wheel so that the contact area during grinding is comparatively small. The pressure available is then sufficie'nt to ensure sharp grinding and no undue heat is generated. v Means fortri'mniin'g the periphery of the wheel is provided and this may consist 'of a diamond or equivalent wheel trimming device "arranged to traverse the length of the wheel, =-cither automatically at suitable intervals, or manually ifdesired. If automatic traverse is provided, au-toin'atic i-n-feed of the trimming device is provided. Trimming may be controlled by a clock or like timing deviceso as to take :place -'at regular intervals, determined in thefirstplace by experiment.

.Other features of theinvention, including a quick-release device for securing the wheel in position, will be explained in the following description with reference to the accompanying drawings in which: t

Figure 1 is a front view of a cutter head of a machine of the kind described showing the position of the grinding wheelwith respect to the knives.

Figure 2 is a viewof .part -of Figure 1 looking down in the direction of the arrow A and showing details of the wheelmounting.

Figure 3 is a front elevation of Figure 2.

Figure 3A is -a section on AA of Figure 3 showing details of a bell crank lever illustrated in Figure 3.

Figure 4 is a section of Figure 2 generally along the line Figure 5 is a front view of part of Figure 4.

Figure 6 is a view of part of Figure 3 looking in the direction of the arrow B.

Figure 7 is a sectional view showing a modified construction of a part shown in Figure 3.

Figure 8 is a circuit diagram of a switching arrangement for traversing a grinding wheel trimming device shown in Figure 3.

Referring first to Figure 1, knives 1 are mounted on a cutter head 2 which rotates in the direction of the arrow so that the knives sweep across a mouth 3 through which a cheese of tobacco leaves is fed. As the knives wear owing to grinding they are automatically fed forwards to keep the edges in the proper cutting plane. A grinding wheel is shown at 4 and is a cylindrical wheel with its axis vertical. This disposition of the axis is preferable for simplicity of manufacture and the collection of dust but is in no way limiting.

Referring now to the remaining figures, a plate 5 Figure 2 is flush with the front of the machine frame and it will be noted that the grinding wheel 4 protrudes slightly through an aperture 6 in the plate. The point marked X is in the cutting plane of the machine.

The grinding wheel 4 is supported for rotation in a frame 7 which is pivoted on a tubular shaft 8 to the frame 9 of the machine and the grinding wheel 4 is advanced to compensate for trimming by a screw and nut device consisting of a screw 10 fixed to a sleeve 11 pivoted on a fixed shaft '12 and threaded into a rotatable nut 13 pivotally mounted in the frame '7, see Figure 4. Operation of the wheel feeding device will be described later.

The grinding wheel 4 is fixed on a stub shaft 14, journalled the upper part of the frame 7, see Figure 3, and driven by .a motor 15, the lower end of the wheel being supported by another stub shaft 16 journalled in the lower ,part. of the frame 7. Each stub-shaft is tapered at 17 and the wheel core is correspondingly tapered so thatwhen the stub shaft tapers are urged towards "one another the wheel is firmly and truly supported and held. Forsafety in driving the wheel, a key 18 is also provided. The relative movement of the stub shafts is eifccted by movement of the lower stub shaft 1621s will now be described. The shaft is journalled in a slidable bush .19 provided with rackteeth 2t engaging a pinion 21 which is fixed on a spindle 22 rotatable by a hand crank 23. If the handle 24 is pressed down, the stub shaft 16 is forced upwards until all the tapers are in close engagement. Then the pinion is locked in position by fixing the position of a quadrant 25 secured to "the crank 23. For this purpose the quadrant is provided with a slot 25A through which passes a screw, the shank 25B of which is shown dotted. The screw is loosened when 'it is required to move the hand crank and tightened when 'the tapers have been properly engagedi This engagement of the tapers is obviously adequate for wheel driving but the key 18 is provided for safety in case the machine attendant does not fix the wheel properly by the stub shaft movement. It' is pointed out that this quick release device is'in the nature of a refinement since a wheel will last many months "but there is not much room inside the machine, and removal of the wheel from a long spindle would be rather inconvenient.

The wheel trimmer is shown in Figure 3 and consists of a diamond 26 mounted ina holder 27 which consists of a screw-threaded rod 28. The screw '28 is naturallyof veryfinepitch and is therefore protected from dust at h I 3 each end by bellows 29. Rotation of the screw 28 is effected by a ratchet wheel 30 and pawl 31, see Figure 6, a description of the action being deferred for the present.

The screw'28 is threaded in a large nut or carriage 32, which is traversed to and fro' parallel tothewheel by a long screw 33 journalled in the frame 7. This screw is also protected by bellows 34. On a bracket 35 above the top end of the screw is fitted an electric motor 70 but whose spindle 71 is coupled to the screw by an Oldham coupling connection at 36. 7

The operation of the whole arrangement will now be described and the remaining parts will be mentioned as they come into operation.

The diamond 26 is normally at rest below-the grinding wheel 4 in Figure 3, which is being rotated by the electric motor 15.

When the grinding wheel 4 requires to be trimmed the motor driving the screw 33 is started. Starting may be effected by manual switching or by a clock-controlled switch according to requirements as found by practice. As the motor starts, the carriage 32 moves upwards and the diamond traverses the length of the wheel until an abutment 37, Figure 2, fixed to the carriage strikes a push rod 38 which operates a microswitch 39 and reverses the motor so that the diamond then makes a downward traverse.

As the diamond reaches the top of its stroke a bevelled face 37A of the abutment 37 comes into contact with a pin 40 and moves it to cause advance of the wheel. The pin 40 is shown displaced in Figure 2 and in Figure 4 in its position of rest.

A suitable switching arrangement is shown on Figure 8 and the parts operate in the following manner. The parts are at rest with trimmer down, and bottom switch 84 is open. As the cam 82 closes switch 83 (shorting 84), current can flow to the shunt field of motor 70 and to its armature through double pole switch 85. The mo tor starts and as the trimmer moves up switch 84 will close and the disengagement of switch 83 will not matter. As the trimmer strikes switch 39 a circuit is made to a magnet 90 which changes over switch 85 and reverses armature current and thus the motor. Magnet 90 also closes upper arm of switch 85 to a magnet circuit contact 91, and the magnet stays live although trimmer comes down. Bottom switch 84 breaks and the whole circuit is dead because the cam 82 has moved on in the time interval of four minutes taken for the trim. The shaft 80 may be a slow speed shaft (slightly more than one revolution per hour) on the tobacco cutter, or the shaft 80 may be driven by a clock mechanism. Various cams 82 may be secured in selected positions on disc 81, fixed on shaft 80.

Referring to Figures 4 and the nut 13 has a ratchet wheel 41 fixed to it. A pawl 42 is pivoted on a ring 43 and urged by a spring 44 into engagement with the ratchet teeth. Thus when the ring is rotated in the direction of the arrow, Figure 5, the ratchet wheel is turned and the nut 13 is unscrewed a trifle off the screw 10. Rotation of the ring is effected by the aforesaid bevel 37A on the abutment 37, the pin 40 being fixed to the ring. As the diamond goes down again the pin 40 is released and the ring 43 is pulled back to the position shown in Figures 4 and 5 by a spring 45. At the back of the ratchet wheel is a gear wheel 46 meshing with another gear wheel 47 so that by turning the latter by a collar 48, Figure 4, the nut 13 may be screwed back fully on to the screw when a new grinding wheel is fitted, so that feeding of the new wheel may start again from the initial position. An indicator may be fitted to show the amount of useful wheel left at any period. This is shown in Figure 2 and consists of a pointer 72 fixed to the frame '9 and a scale 73 attached to the swinging frame 7.

As the diamond approaches the end of the downward traverse and is clear of the grinding wheel 4 the pawl 31 is operated to cause in-feeding of the diamond. For this purpose the pawl 31 is pivoted on a rocking quadrant. 49

pivoted on the diamond feed screw axis. A toe 50 on the quadrant strikes a bell crank lever 51 pivoted at 52. One arm 53 of the lever abuts a stop 54 while the other marked 55 in Figure 3 is shaped as a sharp tooth adapted to engage the toe 50 and rotate the pawl quadrant. A spring 77, Figure 3A, holds'the arm 53 against the stop" 54. Thus a'sthe quadrant travels down, the toe 50 encounters the tooth 55 and the quadrant 49 is caused to rotate and drive the ratchet wheel 30 to feed the diamond in. 7 On further downward movement of the quadrant the toe slips past the tooth 55 and on the next upward movement of the diamond the bellcrank 51 merely turns on its pivot 52 against the action of the bellcrank spring as the toe 50 on the quadrant 49 meets the arm 53.

The carriage 32 has rollers 56, Figure 2, which run on guides 57 and 58 and prevent the carriage from any rotary movement around the screw axis and thus ensuring that the diamond travels in a straight line. Alternatively, as shown in Figure 7, the carriage somewhat altered in shape and bearing reference 74 may be guided by a fixed rod 75 parallel to the screw 33 in which case all the parts can be enclosed in a bellows 76.

At 59, Figure 2, is shown a suction duct for removing dust and metal particles from the neighbourhood of the grinding wheel. A hood 60 attached to the duct surrounds the back of the wheel while auxiliary hood pieces 61 and 62 are attached to the frame 7 and thus move with the advancing grinding wheel. Small spaces are therefore left at 61A and 62A but as air goes inwards towards the duct through these spaces any dust in these regions will pass into the duct and as the wheel is rather a close fit in the aperture 6 the spaces are desirable to prevent too much throttling of the suction. The hood 59 may be bent so as to lie well away from the wheel from the central part at the top of Figure 3 and then curve in again to approach the wheel near the diamond so as to provide a large space within the hood into which particles of Wheel and metal may be thrown by the spinning wheel.

A spring detent device consisting of a double-armed lever pivoted at 63 engages by an arm 64 a serrated wheel 65 fixed to the ratchet wheel 30. A spring (not shown) presses the arm 66 upwards in Figure 3. As the serrated wheel is rotated, the arm 64 merely jumps from notch to notch but its engagement is firm enough to prevent aceidental movement of the diamond holder 26.

The knife blades contact the wheel along the line x-y, Figure 3.

What we claim as our invention and desire to secure by Letters Patent is:

1. In a tobacco cutting machine of the type provided with a cutter head, means supporting said cutter head for rotation on a fixed axis, and a plurality of cutting blades mounted on said head in circumferentially spaced relation about the axis of said head, each blade having a cutting edge extending substantially radially of tile axis of said head, and being of substantial width, whereby said blade edges move in a plane normal to the axis of said head to cut successive slices from a cheese of tobacco leaves fed toward said plane, means for sharpening the cutting edges of said blades comprising a grinding wheel having a cylindrical grinding surface, means supporting said wheel for rotation on an axis transverse to the axis of said head in tangential relation with the said plane and in a position such that the edge of each blade engages the grinding surface with substantially a point contact progressing from one end of the blade edge to the other, and progressing along an element of the cylindrical surface of said wheel, as the blade moves past said wheel.

2. A machine as claimed in claim 1 comprising means for trimming the cylindrical surface of the grinding wheel including a wheel trimming device arranged to traverse the length of the wheel at suitable intervals,

5 said Wheel supporting means being mounted for movement to move the grinding Wheel after trimming, again into tangential relationship with said plane, and mechanism operated by the traversing wheel trimming device for so moving said wheel supporting means.

References Cited in the file of this patent UNITED STATES PATENTS 142,936 Nelson Sept. 16, 1873 764,543 Alsted July 12, 1904 2,271,013 Indge Jan. 27, 1942 2,292,269 Gooch Aug. 4, 1942 2,535,672 Dearsley Dec. 26, 1950 

